The present invention relates to methods and apparatus for the synthesis, recovery, and separation of fullerenes. More particularly, this invention relates to a method for producing fullerenes in large quantities by thermo-cracking of liquid hydrocarbon contained waste products such as motor oil or other hydro-carbon liquids.
Until recently, only two forms of carbon crystalline arrangements were known, namely graphite and diamond. In 1985 Robert F. Curl and Richard E. Smalley of Rice University in conjunction with Harold W. Kroto of University of Sussex reported that a new form of carbon can be made by laser irradiation of a graphite electrode to produce a soot in an evaporation chamber. [C60 Buckminsterfullerene, Nature 318, 162-163, 1985]. Fullerenes are now successfully synthesized and identified by many researchers. Basically, C60 fullerenes are hollow all-carbon cage molecules of 20 six-membered rings and 12 five-membered rings having the general shape of a soccer ball. Fullerenes have the general formula Cn, where xe2x80x9cnxe2x80x9d is an even integer from 60 to 960 (preferably from 60 to 90) atoms all having a shape indicative of a geodesic dome. This is why the name xe2x80x9cfullerenexe2x80x9d was chosen in honor of American architect R. Buckminster Fuller for his structure of the geodesic dome at the 1967 Montreal World Exhibition. The molecules also are called xe2x80x9cbuckminsterfullerenesxe2x80x9d or xe2x80x9cbuckyballsxe2x80x9d. The molecules containing 60 or 70 carbon atoms (C60, and C70) are considered to be the most important due to their high stability and applicability, however higher fullerenes also have significant applications.
Buckyballs have captured the attention of many scientists in the World and have generated considerable coverage by the scientific and popular press. In 1990 at a conference in Germany W. Kratschmer and D. Huffinan announced that they found a simpler way to produce the mixture of C60, and C70 by striking an arc between two graphite electrodes and forming soot (particulate carbonaceous material rich fullerenes) from vaporized carbon. The method is reasonably simple but the production rate is low, obtaining only about 1 gram/hour.
Fullerenes as carbon-cage molecules can be doped with different elements and depending on the cage xe2x80x9ctenantxe2x80x9d find many potential applications in industry. These applications include: development of new solid and liquid lubricants, new coating procedures, water treatment activities, new optical devices, new superconductive materials, new cell batteries, new polymers, new photo-conductive materials, synthesis of drugs, and new materials for the semiconductor industry.
To date, fullerenes are synthesized using graphite electrodes subjected to electric arc discharge, plasma, or laser beam exposure: U.S. Pat. Nos. 5,300,203, 5,393,955, 5,304,366, 5,493,094, 5,227,038, where, according to the prior art, vaporized carbon was condensed and collected as a solid soot from which fullerenes were extracted by column chromatography. Later on, these processes were improved by introducing a sputtering method disclosed in U.S. Pat. No. 5,494,558, where fullerene-containing soot was prepared by bombardment of a carbon target with a sufficient amount of positive ions in the presence of an inert gas and a gas combustion method disclosed in U.S. Pat. No. 5,273,729, where fullerenes can be produced by burning carbon-contained compounds in a flame and collecting the condensibles. These two methods represent significant departures from graphite electrode methods but the production rate of all these methods is still extremely low.
The commercial use of fullerenes suffers from the inability of prior art methods to produce fullerenes in a large quantities and at economical prices.
The present invention provides a novel method for producing fullerenes in large quantities and at lower prices.
The present invention also provides a method which can be scaled to make commercial quantities of fullerenes.
Other disadvantages of the prior art also are overcome by the present invention which provides a method for fullerene production employing an electric arc, a plasma or a laser beam utilizing any carbon-contained waste liquid material such as waste motor oil, or other oils, crude petroleum, or hydrocarbon byproducts of petrochemical cracking.
The present invention employs a liquid phase of waste hydrocarbon hazardous materials as well as other hydrocarbon materials which materials are introduced into a plasma, a laser, or an electrical arc reactor source and which source is employed to strike the surface of the bulk liquid phase to thermo crack or dissociate the material. During thermo-cracking or dissociation of the liquid phase of the hydrocarbon material a mixture of burning gases and carbon vapor is formed. This mixture of gases appears as a cloud. In this cloud atoms of carbon establish bonds and recombine to form fullerenes. After quenching or condensation of the cloud a solid soot is formed in the reactor while a condensed burning gas is discharged from the reactor and is collected for further utilization.
One novel aspect of this invention is in the formation of large amount of fullerenes from liquid waste hydrocarbons and gas materials. The heating or high energy sources such as the plasma gun, the laser beam, or electric arc dissociate the hydrocarbons in the high temperature zone of the reactor in the absence of oxygen and produce carbon vapor and gas formed as a cloud where fullerenes are formed which then is quenched in a condensor zone of the reactor to form a mixture of solid soot, fullerenes and residue gases. By controlling the operational parameters (power, voltage and current) of the plasma jet, laser beam, or electric arc the process can enhance the efficiency of fullerene formation. The main advantages of this process are the significant rate (a few orders of magnitude higher) of fullerene formation at lower cost, and the ability to scale up production.
A better understanding of the invention will be obtained from the following detailed description and the accompanying drawings of illustrative application on the invention.